[andyjohnson0]

Not really answering your question, but as far as I know panel lifetime is largely determined by cumulative damage from the environment. Scratches from trees, etc. reduce effectiveness, as does rain leaking into the panel through gaps created by the daily thermal cycle. There may be a lot of scope for extending their lifetime by improving packing, which would defer the environmental impact of recycling. There is some info on these factors in [1].

Also, panels may be declared end-of-life because they are not as effective as newer ones, even though they are still generating to original specification.

[1] http://energyinformative.org/lifespan-solar-panels/